Plastic blow molded bottles for holding water such as disclosed by U.S. Pat. No. 5,732,838 Young must be designed to withstand internal pressure that is utilized to provide the filled bottle with rigidity. This internal pressure is normally only about one-half to one atmospheric gauge pressure and is thus substantially less than the pressure held by bottles that hold carbonated beverages. Nevertheless, the lower base on which the water bottle sits must be constructed so that its conventional upwardly extending central portion does not invert downwardly because of the internal pressure.